Chair adjustment mechanism



Nov. 19, 1963 r M. E. PEARSON 3,111,343

CHAIR ADJUSTMENT MECHANISM 5 Sheets-Sheet 1 'FIGJ. FICLE.

Filed May 12. 1961 FIG.3.

no a: IOQ, av 22 3b [IO 25: I I I 9 30. 25b as 3 a e. 34 23b 23INVENTOR. MAXWELL E. PEARS ON.

Nov. 19, 1963 M. E. PEARSON 3,111,343

CHAIR ADJUSTMENT MECHANISM Filed May 12, 1961 v s Sheets-Sheet 2 mmvroxMAXWELL E. PEARSON ymncw Nov. 19, 1963 Filed May 12, 1961 XVII M. E.PEARSON 3,111,343

CHAIR ADJUSTMENT MECHANISM 5 Sheets-Sheet 3 INVENTOR. MAXWELL E. PEARSON"lion; )4 M Nov. 19, 1963 M. E. PEARSON 3,111,343

CHAIR ADJUSTMENT MECHANISM Filed May 12, 1961 5 Sheets-Sheet 4 FIG.8.

III n. nlLfllIL 1| 1| 1 INVENTOR.

MAXWELL E. PEARSON 1" B7 rm/Mn Nov. 19, 1963 Filed May 12, 1961 FIG. I2.

FIG. l5.

M. E. PEARSON CHAIR ADJUSTMENT MECHANISM 5 Sheets-Sheet 5 I NVENTOR.MAXWELL E, PEARSON "254a D VQZW ATTOKA/f) United States Patent 3,111,343Cl im ADEUrlTh/EENT IVEQHANEM Maxwell E. Pearson, Baily, ?a., assign'orto Knoli Associates, The, New York, N.Y., a corporation of New YorkFiled May 12, 1%1, Ser. No. 109,535 18 (Ilaims. (Cl. 297306) Thisinvention relates to chairs, and is particularly concerned with chairswhich are useful in business offices, for example secretarial chairs.

Typical secretarial chairs of the prior art are provided with a backadjustable with respect to the seat. In many chairs, the angularrelationship of the back with respect to the seat may be adjusted andthe height of the back with respect to the seat may be separatelyadjusted. Many such chairs have a tiltable back, spring loaded to aforward position, so that the user of the chair may lean back against ayielding spring. It is common to provide means for adjusting the tensionof such a spring.

The various adjustments for the back angle, back height, and springtension commonly include parts having complex surfaces, such as screwthreads or knurled surfaces. Those parts must necessarily be accessiblefor changing the adjustments to suit the requirements of particularusers of the chair. This accessibility has commonly been secured byplacing the adjustable parts where they are readily visible. The partsin question are usually unsightly, and their complex surfaces providemany small areas which are subject to deposit of dust and dirt, makingthem even more unsightly.

An object of the present invention is to provide an improved chair seatconstruction.

Another object of the invention is to provide a chair having a seat anda back, and improved means for ad justing the angular relationshipbetween the back and the seat.

Another object is to provide, in a chair of the type described, improvedmeans for adjusting the height of the back relative to the seat.

Another object is to provide in a chair having a yielda'ole back,improved means for controlling the spring tension which biases the backtoward its normal angular position with respect to the seat.

It is a further object of the present invention to provide a chair ofthe type described in which all the adjustments are made by mechanismswhich are for the most p rt concealed. A further object is to providethose parts of the adjusting mechanism which are not concealed withsimple, smoothly contoured surfaces.

The foregoing and other objects of the invention are attained in thechair described herein, which is adapted for mounting on a base with acentral swivel spindle. On the top of the spindle is mounted a castaluminum shell, generally concave as viewed from the top and open at thetop.

A pivot means including a torsion spring is mounted transversely of theshell and completely inside it. This pivot means includes inner andouter concentric metal sleeves and a rubber member between and bonded toboth sleeves and serving as a torsion spring. A torque arm is fixed tothe outer sleeve and projects rearwardly from it. A lever arm isjournaled on the outer sleeve and also projects rearwardly from itthrough an aperture provided in the shell and beyond the rear edge ofthe seat. The lever arm is provided with a pivotally mounted rearwardextension. The arm and the extension have interengageable gear segments.When the gear segments are engaged, the angular position of the rearextension is fixed. Engagement and disengagement of the gear segments isaccomplished by rotating the pivot pin, which has an eccentric engagingthe extension.

The rear section of the lever arm is apertured to receive an uprightwhich carries the back structure.

A wedge member is insertable into the aperture through an openingprovided in the rear extension of the lever arm. The wedge is operableeither to lock the upright against vertical movement or to release itfor adjustment of the back h ight.

The eccentric for releasing the back angle adjustment is operated by aknob fixed on one end of the pivot pin for the rear extension of thelever arm. Another knob threaded on the opposite end of the pivot pin isoperable both to lock the back angle adjustment and the locking Wedgefor the height adjustment.

Other objects and advantages of the invention will become apparent froma consideration of the following specification and claims, takentogether with the accompanying drawings.

In the drawings:

FIG. 1 is a side elevational view of a chair embodying the invention;

PEG. 2 is a plan view taken on the 1 with the seat removed;

FIG. 3 is a view partly in elevation and partly in section on the lineiii-i i of H6. 2, showing the back angle adjustment mechanism and thespring tension adustment;

4 is a view, partly in perspective and partly in section on the line ik-V of PEG. 2, showing the seat attaching clips;

FIG. 4A is a cross-sectional view showing one of the retainers for theseat attaching clips;

ELL? 5 is a plan view of the seat supporting shell with the seatremoved;

PEG. 6 is a crosssection view of the shell shown in 5, taken on the ins.VlVI of FIG. 5, and with certain parts removed;

FIG. 7 is a perspective View showing the shell of FIG. 5 with angleplates mounted thereon to serve as supports for the back supportin leverarm pivot;

Fit 8 is a view partly in plan and partly in section on the Viii-/lli ofFIG. 9 of the front section of the lev arm with all other parts removed;

FIG. 9 is an elevational view of one half of the lever arm of FIG. 8,taken on the line 1XlX of FIG. 8;

FIG. 10 is a perspective view of a connecting pin shown in dotted linesin FIG. 8;

mi 1G. 10A is a cross-sectional view of the pin of FIG.

FIG. 11 is a cross-section view taken on the line Xi-Xl of PEG. 9;

FIG. 12 is a cross-sectional view taken on the line iilXil of FIG. 1;

FIG. 13 is an eievational view of the rearward section of the lever armtaken on the line X HXHI of FIG. 12;

PEG. 14 is a sectional view, taken through the pivot axis of the is erarm, looking upward;

i6. 15 is a fragmentary view showing stop structures which limitrotation of a control knob;

FIG. 16 is a fragmentary front elevational view, showing the generalcontour of the seat and seat supporting shell;

PEG. i7 is a fragmentary sectional view, taken on the line XViiXVil ofPEG. 14, illustrating a detail;

FIG. 18 is a plan View of one of the plates for mounting the lever armpivot; and

FIG. 19 is an elevational view of the plate of FIG. 18.

PEG. 1 illustrates a chair including a base 1 in which is journaled avertical spindle 2. A shell 3 is supported on the top of the spindle 2and in turn supports a seat cushion 4. A lever arm 24 extends rearwardlyfrom the line 11-1! of FIG.

shell 3, and has a rearward extension 25 which supports an upright 6which carries the back '7 of the chair.

The base 1 and the spindle 2 form no part of the present invention, andare shown only generally in the drawings. The base 1 and spindle 2 maybe provided with a suitable height adjustment mechanism (not shown).Spindle 2 is enclosed within a dust shield 5.

The shell 3 is shown in detail in FIGS. 5 and 6. The shell 3 has aconcave upper surface, and is open at the top. Two reinforcing ribs 3extend from the front rim of the shell to the back rim. Two otherreinforcing ribs 9 extend from one side rim of the shell to the other.Ribs 8 and 9 and the rim of the shell provide a smoothly contouredsurface for supporting a base plate ltl (FIGS. 3 and 4) on which ismounted the seat cushion 4.

The shell 3 may be of cast aluminum or other suitable material. The seatplate It may be of a reinforced plastic material which is somewhatflexible, for example, Masonite.

The shell 3 is provided near its lowest portion with a hub 3a (HG. 6)having a central aperture 3b adapted to receive the upper end of thespindle 2.

The seat plate 1b is apertured to receive a plurality of spring clips 11(HG. 4), each having an end Illa which extends below the seat plate 1%)and projects horizontally, so as to be generally parallel with the seatplate it In the shell 3, adjacent the ribs 9 are a plurality of bosses12, each provided in its upper surface with two spaced apertures 12a forreceiving a leg of a U-shaped spring retainer 13. The central portion ofthe retainer 13 extends above the upper surface of the rib 9.

Near the rear edge of the shell 3, along its centerline, there isprovided an upwardly extending projection 3c (FIG. 3) which is adaptedto be received in an opening a formed in the seat plate 16.

The seat, including the cushion 4 and the plate It may be assembled onthe shell 3 by sliding the seat forwardly along the top of the shell sothat the clip ends Ila slide between the central portions of theU-shaped retainer 13 and the tops of the bosses 12. The projection 3cand the aperture 163a are so placed that when the edge of the seat isaligned with the edge of the rim, the projection 30 snaps into theaperture lilo. During the horizontal movement of the seat, the plate it)must be suiticiently flexible to bend and accommodate the movement ofthe seat plate 10 past the projection 36.

The rim of the shell 3 is protected by a rubber ring 14 (FIG. 3) havinga generally U-shaped cross-section. This rim may be formed as a rubberextrusion, which is cut in lengths somewhat shorter than the perimeterof the shell. The ends of each length are then vulcanized together toform a ring and the ring is stretched over the shell rim. The rubberring 14- provides a smooth and resilient surface which may receiveimpacts from adjacent objects without being marred or damaged.

On either side of the hub 3a, the shell 3 is provided with a pair ofbosses 15 (FIG. 5) in which are formed screw holes 15a. Another pair ofbosses 16 are provided in the shell 3 at localities spaced to the rearand to the side from the bosses 15. The bosses 16 are also provided withscrew holes 16a. A pair of angle plates 17 (see FIGS. 7, 14, 18 and 19)are supported on the bosses 15 and 16 and are held in place by 5 rowsextending through the plates and into the bosses. The angle plates 17are provided with downwardly depending portions 17a which are adapted toreceive the ends of a bolt 18 (see FIG. 14). The bolt 18 is provided atone end with a head which abuts the outside of one of the angle plates17. The opposite end of the boltlS is threaded to receive a nut lMounted on the bolt 13 between the plates 17 is a torsion springincluding an inner sleeve 20', and an outer sleeve 21, separated by arubber torsion spring member 22 which is bonded to both the inner sleeve2d and the outer sleeve 21. The term rubber is used herein as a genericterm including natural rubber and any of the synthetic rubbers whichhave equivalent or superior stretching properties. in the plates 17,adjacent the apertures which receive the bolt 18, there are providedinwardly projecting indentations 17b (FIG. 17), which engagecorrespondingly formed grooves in the ends of the inner sleeve 2t). Theindentations 17b and the grooves serve as keys to lock the inner sleeve2%) against rotation with respect to the plates 17.

On the outer surface of the outer sleeve 21, at its middle portion,there is fixed a torque arm 23. The torque arm 2-3 may be fixed to thesleeve 21 by a plastic bonding agent or other suitable means. The arm 23projects rearwardiy from the sleeve 21 and is provided at its rear endwith an aperture 23:: for receiving a screw 235, whose slotted screwhead is at the lower end of the screw.

The lever arm 24-, best seen in FIGS. 8 to 11, is pivotally mounted (seeFIG. 14-) on the outer sleeve 21, and its rearward extension 25, bestseen in FIGS. 3 and 12, is pivotally mounted (see P10. 12) on a pivotpin 26 journaled on the rear end of the lever arm 2 The lever arm 24 isbuilt up from two parts 24a, 24b of generally channel shapedcross-section (see FIGS. 8 and 11). Near their centers, the two parts24a, 2452 are provided with two holes 27 (FIG. 9), each adapted toreceive a V-notched pin 28. Each V-notched pin 28 (FIG. 10) is made witha slightly larger diameter than the holes 27 and is driven into one ofthe holes, thereby compressing its V-shaped notch, which extends thefull length of the pin. After two pins are inserted in one of the parts2%, 24b, the other of the two parts is then assembled on the pins bysimply forcing it on, and the compression of the V-shaped notches in thepins holds the pins and the two parts 24a and 24b tightly together.

Each of the parts 24a, 24b has a projection 24c adapted to be receivedin a corresponding recess 24d on the other one of the two parts. Theinterlocking projection 24c and recess 24d cooperate to prevent relativemotion between the parts 24a, 24b.

The complete lever arm 24, as seen in FIG. 8, is bifurcated at its frontend to provide two hubs 29, which are journaled for rotation on theouter sleeve 21, which serves as a pivot means for the lever arm. Eachof the hubs 29 carries two projections 3t 31 (FIG. 9), which cooperatewith the seat plate ill and the shell 3 respectively to limit therotation of the lever arm 24.

The lever arm 24 extends rearwardly through an aperture 302 in the shell3, best seen in FIG. 6.

The rear end of the lever arm 24 is also bifurcated to provide two hubs32, which are apertured to receive the pivot pin 26 (see FIGS. 8 and12).

The two parts 24a, 24b are placed together with the flanges of theirchannel shaped cross-sections abutting, as shown in FIG. 11. On theunder side of the abutting upper flanges, there is attached, as bywelding, a wear plate 33 against which the screw 23b abuts (see PEG. 3).The lower flanges of the parts 24a and 24b opposite the wear plate 33are apertured to provide an access opening 34- through which the screw 2may be reached to adjust the spring tension which is biasing the torquearm 23 clockwise as viewed in FIG. 3, and thus biasing the front section24 of the lever arm clockwise to hold the projections 3% and 31 againstthe shell 3.

The rear extension 25 of the lever arm includes a forwardly projectingportion 35 (FIGS. 12 and 13) provided at its front end with a gearsegment 35a adapted to engage a gear segment 36 (see FIG. 9) formed onthe front section 24 of the lever arm.

The rear extension 25 of the lever arm also comprises a hub 25a which isjournaled on an eccentric portion 26a (FIG. 12) of the pivot pin 26. Tothe rear of the pivot pin 26, the rear extension 25 includes a portion25b. Extending generally vertically through the portion 25b is anaperture 250 of generally wedge-shaped horizontal cross-section, as bestseen in FIG. 12. The upright 6 which carries the back 7 extends throughthe aperture 25c, and similarly has a generally wedge-shapedcrosssection, as seen in FIG. 12. The aperture 250 is slightly longerfrom front to back than the upright 6 and is slightly wider at itswidest or front end. A washer 37 is received in a recess on one side ofthe arm extension 25 and is provided with a tongue 37a having a taperedtip which projects through an opening in the arm extension 25 and intothe aperture which receives the upright 6.

The pivot pin 26 is provided on one end with an enlargement 26b whichserves as a knob for rotating the pin 2 5. Another knob 38 is fixed on ascrew 39 which is threaded into an internally threaded hole extendingalong the axis of the pin 26 at the end opposite the knob 2617.

When the knob 38 is rotated and tightened against the washer 37, thenthe tongue 37a is forced into the aperture 25c and drives the upright 6toward the narrow end of the wedge-shaped aperture, thereby wedging theupright 6 against vertical movement. The parts are shown in thistightened position in FIG. 12. At the same time, the knob 26 and theknob 38 compressively engage the hubs 32 of the lever arm 24, so thatthe pin 26 is held against rotation.

When it is desired to change the angular position or the height of theback, the knob 38 is loosened, thereby allowing the tongue 37:: to slipout of the aperture 250. '1'" he upright 6 can then be moved up or downto set the back 7 at the required new position. While the nut 38 isloosened, the knob 26b may be rotated to move the eccentric from theposition shown in FIG. 12 to a position which moves the lever armextension 25 rearwardly and disengages the gear segment 35a from thegear segmeat 36. As soon as the gear segments are disengaged, the armextension 25 may be rotated on the eccentric 26a to any new angularposition desired within the range (best shown in FIG. 13) permitted bythe top and bottom flanges of the lever arm sections 24a and 24b. Afterthe back is positioned in its desired angular relationship with respectto the seat, the knob 26b may again be rotated one-half turn to bringthe gear segments 35a and 36 into engagement, thereby fixing the newangular position. The lever arm sections 24 and 25 may then be lockedagainst relative movement by tightening the knob 38, which also drivesthe tongue 37a into the aperture 250 and locks the upright 6 againstvertical movement.

The knob 2o!) carries two inwardly projecting stops that, 4% on the rimof the knob. T'hese stops 49a, 49b cooperate with a fixed stop 41carried by the 'arm 24a (see FIG. 9). When the knob 26 is in the angularposition shown in FIG. 15, the eccentric 26a has moved the rear armsection 25 to the forwardmost point of its travel, so that the earsegments 35a and '36 are fully engaged. A person changing the back angleadjustment on the chair will tend to move the knob 26b as far as it willgo, he ever, thereby carrying the stop dfia past the position shown inFIG. 15 until it abuts against the fixed stop 41. This carries theeccentric 26:: past the point of maximum inward movement of the arm 25and sepwates the gear segments 35:: and 35 slightly. This slightseparation serves as a safety lock, so that the angular position willnot change due to vibration of the chair. In order for the gear segmentsto be released from this look, the knob 26b must be rotated in adirection such that the initial movement of the arm 25 will tend totighten the gear segments 35:: and 35 more close y together. When it isdesired to change the back angle adjustment, the knob 26b is rotated onehalf turn, until the stop 4% strikes the fixed stop 51. At that positionof the eccentric 26a, the gear segments 35a and 36 are disengaged, andthe rear arm extension 25 is free to rotate on the eccentric 26a.

l Vhile I have shown and described a preferred embodiment of myinvention, other modifications thereof will readily occur to thoseskilled in the art and I therefore intend my invention to be limitedonly by the appended claims.

I claim:

1. A chair, comprising a seat, a frame supporting said seat, a back, anupright supporting said back, a first arm supported on said frame andextending rearwardly therefrom, a second arm supporting said upright,:pivot means supporting the second arm on the rear end of the first arm,said arms having parts interengageable in different angular positions ofthe second arm relative to the first arm, and means for shifting saidsecond arm from a for ward position in which said parts are interengagedto prevent angular movement of the second arm on said pivot means to areanward position in which said parts are disengaged and said second armis angularly movable on the pivot means to change the angularrelationship between the back and the seat.

2. A chair as defined in claim 1, in which said interenga eable partsare gear segments.

3. A chair as defined in claim 1, in which said pivot means comprises apin having a first cylindrical portion journaled in said first arm, anda second cylindrical portion eccentric with respect to said firstcylindrical portion and journaled in said second arm, and said means forshifting said second arm comprises a knob for rotating said pin in saidfirst arm between first and second angularly spaced positionscorresponding respectively to the forward and rearward positions of thesecond arm, and means operable to lock said pin in said first position.

4. A chair as defined in claim 3, including stop means to limit therotation of the pin to one-half revolution, said first angularly spacedposition of the pin corresponding to the center of said one halfrevolution.

5. A chair as defined in claim 1, in which: said first arm is bifurcatedat its rearward end to provide two horizontally spaced members; saidsecond arm is located between said spaced members; and said pivot meanscomprises a pin leaving two spaced, aligned cylindrical portionsjournaled in said spaced members and a third cylindrical portioneccentric with respect to said two portions and journaled in said secondarm.

6. A chair as defined in claim 5, in which said means for shifting saidsecond arm comprises a first knob fixed on one end of said pin forrotating said pin in said first arm between first and second angularlyspaced positions corresponding in which the eccentric portion of the pinis effective to establish the second arm respectively in its fonward andrearward positions, and a second knob threaded on the other end of saidpin and rotatable to clamp the two members between the knobs and therebyto lock the pin in its first angular position.

7. A chair, comprising a seat, a frame supporting said seat, a back, anuprigirt supporting said back, said upright having a generallywedge-shaped cross-section, an arm supported on the seat frame andextending rearwardly therefrom, said arm having a vertically extendingaperture adjacent its rearward end, said aperture having a cross-sectionsimilar to that of the upright but wider at its widest end and slightlylonger, said upright being received in said aperture, a wedge memberinsertable in said widest end to drive the upright toward the narrow endof the aperture and thereby to wedge the upright against verticalmovement, and means for moving the wedge member between its insertedposition and a retracted position wherein it allows free verticalmovement of the back and upright.

8. A chair, comprising a seat, a frame supporting said seat, a back, anupright supporting said back; means for varying the angular relationshipof the back relative to the seat, including a first armsupported on saidframe and extending rearwardly therefrom, a second arm supporting saidupright, pivot means supporting the second arm on the rear end of thefirst am, said arms having parts interengageable in different angularpositions of the second arm relative to the first arm, and means forshifting said second am from a forward position in which said parts areinterengaged to prevent angular movement of the second arm on said pivotmeans to a rearward position in which said parts are disengaged and saidsecond arm is :angularly movable on the pivot means to change theangular relationship between the back and th seat; means for varying theheight of the back relative to the seat, including a portion of saidupright having a generally wedge-shaped cross-section, a portion of saidsecond arm having a vertically extending aperture adjacent its rearwardend, said aperture having a cross-section similar to that of the uprightbut wider at its widest end and slightly longer, said upright portionbeing received in said aperture, a wedge member insertable in saidwidest end to drive the upright toward the narrow end of the apertureand thereby to wedge the upright against ventical movement, and meansfor moving the wedge member between its inserted position and aretracted position wherein it allows free vertical movement of the backand upright; and means operated concurrently with movement of the wedgemember to its inserted position to lock said second arm in its forwardposition, the eby fixing the height and angular relationship of the backrelative to the seat.

9. A chair as defined in claim 8, in which said pivot means comprises a:pin extending through said first and second arms, said means to locksaid second arn comprises a nut threaded on said pin; said wedge membermoving means comprises a washer encircling said pin; and said wedgemember comprises a tongue projecting from said washer toward said widestend of the aperture, said tongue being moved by tightening of the nutinto said aperture to wedge the upright against vertical move ment, saidpin being locked against angular movement by tightening the nut againstthe adjacent one of said arms.

10. A chair, comprising a base, a shell open at the top and having inits under surface a recess for receiving the upper portion of the base,a seat, means for attaching the seat to the shell to close the open topthereof, pivot means extending transversely of the shell includingconcentric inner and outer sleeves and a rubber torsion spring memberbetween and bonded to said sleeves, a torque arm fixed to the outersleeve and projecting outwardly therefrom, means connecting the innersleeve to the frame -including key means to prevent relative rotation ofthe inner sleeve and frame, a first supporting arm journaled on theouter sleeve and extending therefrom rearwardly through an apenture inthe shell, a screw threaded into the outer end of the torque arm andabutting said supporting arirn, stop means to limit the rotation of theback supporting arm with respect to the frame, said screw beingadjustable to vary the force of the torsion spring member tending tohold the supporting arm against said stop means, a back for the chair,an upright supporting the back; and means for varying the angularrelationship between the seat and the back including said supportingarm, a second supporting arm carrying said upright, second pivot meansmounting the second a m on the rear end of the first arm, said armshaving parts interengageable in diiferent angular positions of thesecond arm relative to the first arm, and means for shifting said secondarm from a forward position in which said parts are interengaged .toprevent angular movement of the second arm on said pivot means to arearward position in which said parts are disengaged and said second armis angularly movable on the pivot means to change the angularrelationship between the back and the seat.

11. A chair, comprising a base, a shell open at the top and having inits under surface a recess for receiving the upper portion of the base,a seat, means for attaching the seat to the shell to close the open topthereof, pivot means extending transversely of the shell includingconcentric inner and outer sleeves and a rubber torsion spring memberbetween and bonded to said sleeves, a torque anm fixed to the outersleeve and projecting rearwardly therefrom, means connecting the innersleeve to the frame including key means to prevent relative rotation ofthe inner sleeve and frame, a first supporting arm journaled on theouter sleeve and extending therefrom rearwardly through apenture in theshell, a screw threaded into the outer end. of the torque arm andabuttingsaid supporting arm, stop means to limit the rotation of theback supporting arm with respect to the frame, said screw beingadjustable to vary the force of the torsion spring member tending tohold the supporting against said stop means, a b k for the chair, anupright supporting the back; means for varying the angular relationshipbetween the seat and the back including said supporting arm, a secondsupporting arm carrying said upright, second pivot means mounting thesecond arm on the rear end of the first arm, said arms having partsinterengageable in different angular positions of be second arm relativeto the first arm, and means for shifting said second arm from a forwardposition in which said parts are in-terengaged to prevent angularmovement of the second arm on said pivot means to a rearward position inwhich said parts a e disengaged and said second arm is angularly movableon the pivot means to change the angular relationship between the backand the seat; means for varying the height of the back relative to theseat, including a portion of said second arm having a verticallyextending aperture adjacent its rearward end, said aperture having across-section similar to that of the upright but wider at its widest endand slightly longer, said upright portion being received in saidaperture, a wedge member insertable in said widest end to drive theupright toward the narrow end of the aperture and thereby to wedge theupright against vertical movement, and means for moving the wedge memberbetween its inserted position and a retracted position wherein it allowsfree vertical movement of the back and upright; and means operatedconcurrently with movement of the wedge member to its inserted positionto lock said second arm in its forward position, thereby fixing theheight and angular relationship of the back relative to the seat.

12. A chair comprising a base, a frame supported on said base, torsionspring means including concentric inner and outer sleeves and a rubbertorsion spring member between and bonded to said sleeves, a torque armfixed to one of the sleeves and projecting outwardly therefrom, meansconnecting the other sleeve to the frame including key means to preventrelative rotation of said other sleeve and the frame, a back, an armsupporting the back and journaled on said one sleeve, a screw threadedinto the outer end of the torque arm and abutting said back supportingarm, and stop means to limit the rotation of the back supporting armwith respect to the frame, said screw being adjustable to vary the forceof the torsion spring member tending to hold the back supporting arrnagainst said stop means.

13. A chair as defined in claim 12, in which said one sleeve is theouter sleeve and said other sleeve is the inner sleeve; said backsupporting arm is bifurcated at its forward end to provide twohorizontally spaced members journaled on said outer sleeve on oppositesides of said torque arm, said back supporting arm including a first webconnecting the upper parts of said members, overlying said torque armand abutting said screw, and a second web connecting the lower parts ofthe members and extending under the torque arm and the screw, saidsecond web being apertured to provide access to the head of the screwfor adjusting the force of the torsion spring means.

14. A chair, comprising a base, a frame supported on the base, a seat,means for attaching the seat to the frame, pivot means extendingtransversely of the frame including concentric inner and outer sleevesand a rubber torsion spring member between and bonded to said sleeves, atorque arm fixed to the middle of the outer sleeve and projectingreanwardly therefrom, means connecting the inner sleeve to the frameincluding key means to prevent relative rotation of the inner sleeve andframe, a first supporting arm bifurcated to provide two horizontallyspaced members journaled on the outer sleeve on opposite sides of thetorque arm, said supporting arm extending rearwardly from said membersthrough an aperture in the frame, a screw threaded into the outer end ofthe torque arm and abutting said supporting arm, stop means to limit therotation of the back supporting arm with respect to the frame, saidscrew being adjustable to vary the force of the torsion spring membertending to hold the supporting arm against said stop means, a back forthe chair, an upright supporting the back; means for varying the angularrelationship between the seat and the back including said supportingarm, said supporting arm being bifurcated at its rearward end to providespaced fingers, a second supporting arm carrying said upright, secondpivot means mounting the second arm between the fingers on the rear endof the first arm, said arms having parts interengageable in difierentangular positions of the second arm relative to the first arm, and meansfor shifting said second arm from a forward position in which said partsare interengaged to prevent angular movement of the second arm on saidpivot means to a rearward position in which said parts are disengagedand said second arm is angularly movable on the pivot means to changethe angular relationship between the back and the seat.

15. A chair as defined in claim 14, including means for varying theheight of the back relative to the seat, said height varying meansincluding a portion of said second arm having a vertically extendingaperture adjacent its rearward end, said aperture having a crosssectionsimilar to that of the upright but wider at its widest end and slightlylonger, said upright portion being received in said aperture, a wedgemember insertable in said widest end to drive the upright toward thenarrow end of the aperture and thereby to wedge the upright againstvertical movement, and means for moving the wedge member between itsinserted position and a retracted position wherein it allows freevertical movement of the back and upright; and means operatedconcurrently with movement of the wedge member to its inserted positionto lock said second arm in its forward position,

thereby fixing the height and angular relationship of the back relativeto the seat.

16. A chair, comprising a base, a shell open at the top and having inits under surface a recess for receiving the upper portion of the base,a seat mounted on and covering the top of the shell, pivot meansextending transversely of the shell, means in the shell for mountingsaid pivot means, an arm pivotally supported on said pivot means andextending therefrom rearwardly through an aperture in the shell, a backfor the chair, and means for supporting the back on the rear end of thearm.

17. A chair as defined in claim 16, in which said pivot means includesconcentric inner and outer sleeves and a rubber torsion spring memberbetween and bonded to said sleeves, a torque arm fixed to the outersleeve and projecting outwardly therefrom, means connecting the innersleeve to the shell, including key means to prevent relative rotation ofthe inner sleeve and shell, said arm being journaled on the outersleeve, a screw threaded into the outer end of the torque arm andabutting said back supporting arm, and stop means to limit the rotationof the back supporting arm with respect to the frame, said screw beingadjustable to vary the force of the torsion spring member tending tohold the back supporting arm against said stop means.

18. A chair as defined in claim 16, in which said mounting meanscomprises a pair of angle plates, each angle plate having a horizontalportion and a downward- 1y depending vertical portion, abutment means inthe shell projecting upwardly therefrom and supporting said angleplates, and means fastening the angle plates to the abutment means, saidvertical portions of the angle plates being apertured to receive theends of the pivot means.

References Cited in the file of this patent UNITED STATES PATENTS2,310,476 Todd Feb. 9, 1943 2,437,940 Cramer Mar. 16, 1948 2,584,614Rasmussen Feb. 5, 1952 2,664,305 Hobart Dec. 29, 1953

1. A CHAIR, COMPRISING A SEAT, A FRAME SUPPORTING SAID SEAT, A BACK, ANUPRIGHT SUPPORTING SAID BACK, A FIRST ARM SUPPORTED ON SAID FRAME ANDEXTENDING REARWARDLY THEREFROM, A SECOND ARM SUPPORTING SAID UPRIGHT,PIVOT MEANS SUPPORTING THE SECOND ARM ON THE REAR END OF THE FIRST ARM,SAID ARMS HAVING PARTS INTERENGAGEABLE IN DIFFERENT ANGULAR POSITIONS OFTHE SECOND ARM RELATIVE TO THE FIRST ARM, AND MEANS FOR SHIFTING SAIDSECOND ARM FROM A FOR-